Cells of the gamma delta T cell receptor (TCR) lineage predominate in epithelial tissues. In addition to producing cytokines, they have been shown to elaborate chemokines and epithelial growth factors that can influence inflammation as well as epithelial growth and repair, respectively. These multifunctional attributes of gamma delta intraepithelial lymphocytes (IEL) are unique among lymphocytes. The hypothesis to be tested is whether similar or distinct gamma delta IEL subsets function to regulate inflammation as well as epithelial growth and repair in order to protect and maintain the integrity of the epithelial borders. We will use an infectious murine model of pulmonary epithelial cell injury incorporating normal, gamma delta T cell deficient and adoptive gamma delta T cell recipient mice to define the in vivo pattern of cytokine and growth factor production of gamma delta IEL subset(s). The identification of these soluble factors and their location in situ will delineate the role of gamma delta IEL in inflammation and epithelial repair in the lung. The following three specific aims will be accomplished in order to achieve the research objectives: 1. Cytokine and growth factor production by gamma delta IEL subsets in response to pulmonary epithelial cell damage. Perturbation and/or injury of pulmonary epithelium will be induced by infection with a Nocardia asteroides strain that only binds, or one that both binds and invades pulmonary epithelial cells. The ability of similar or distinct gamma delta IEL subsets to regulate the response to this injury will be assessed by intracellular flow cytometry, immunohistochemical methods, and if necessary, in situ hybridization. 2. The requirement for gamma delta IEL in the response of the lung to varying degrees of pulmonary damage will be measured in TCR delta deficient mice that lack gamma delta T cells. Quantitative measurements of lung injury will be assessed by morphometry in order to precisely characterize the extent of inflammation and epithelial cell damage and repair that occurs or does not in the absence of gamma delta IEL. 3. In vivo modulation of gamma delta IEL and the cytokines they produce to examine the effect of a single component on their response to lung injury. Reconstitution of gamma delta T cell deficient mice with gamma delta IEL from normal, V gamma 1.1 transgenic or cytokine deficient mice will be used to alter or remove one component of the gamma delta IEL response to assess its relative role in inflammation and epithelial repair. The ultimate aim of this research is to realize those factors associated with gamma delta IEL that determine appropriate responsiveness at the epithelial borders of the host.